System to prevent accidental rerecording on a magnetic record



Jan. 23, 1951 s. J. BEGUN 2,538,392

SYSTEM TO PREVENT ACCIDENTAL RECORDING ON A MAGNETIC RECORD Filed Dec.4, 1946 I 5 Sheets-Sheet 1 I N V EN TOR.

- v S.J.BE6UN ?E?85 BYP.E+Z

ATTORNEYS Jan. 23, 1951 2,538,892

S. J. BEGUN SYSTEM TO PREVENT ACCIDENTAL RECORDING ON A MAGNETIC RECORDFiled Dec. 4, 1946 5 Sheets-Sheet 2 INVENTOR. S.J. BEGUN ATTORNEYS Jan.23, 1951 5. J. BEGUN 2,538,892 SYSTEM TO PREVENT, ACCIDENTAL RECORDING 1ON A MAGNETIC RECORD Filed Dec. 4, 1946 5 Sheets-Sheet 3 "w #M'MIA 5457REM/ND FORK/1RD AECORD BACK INVENTOR.

S.J. Basuu ATTORNEYS BEGUN SYSTEM TO PREVENT ACCIDENTAL RECORDING Jan.23, 1951 s. J.

ON A MAGNETIC RECORD 5 Sheets-Sheet 4 Filed Dec. 4, 1946 Pig.

INVENTOR. S. J. BEGUN ATTORNEYS Jan. 23, 1951 s J BEGUN 2,538,892

SYSTEM TO PREVENT ACCIDENTAL RECORDING ON A MAGNETIC RECORD 5Sheets-Sheet 5 Filed Dec. 4, 1946 286 252 22 J v v v v v v =5 l Pw buckINVENTOR S.J.BEGUN BYp 2 f0 ATTORNEY S Patented Jan. 23, 1951 V ,,UNITEDSTATES ATENT QFFECE SYSTEM TO PREVENT ACCIDENTADRE- RECORDING )N AMAGNETIC RECORD Semi J. Begun, Cleveland Heights, Ohio, assignor to TheBrush Development Company, Cleveland, Ohio, a corporation of OhioApplication December 4, 1946, Serial No. 713,963

Fig. 1 illustrates a magnetic recording and reproducing apparatusaccording to the invention; Fig. 1A is an enlarged view of one form ofmagnetic head assembly embodying the invention;

Fig. 2 is a sectional view of the assembly structure of the headassembly of Fig. 1A along line 2-2;

Fig. 3 is a top view of the head construction of Fig. 1A;

Fig. 4 is a side view of a mounting member for one of the magnetic coresof Fig. 1A, the magnetic core being shown in dotted lines;

Fig. 5 is an end view of the mounting member of Fig. 4;

Fig. 6 is a cross-section of the mounting members of Figs. 4 and 5 alongthe line 6-6 and showing the magnetic core;

Fig. 6A is a cross-section of the mounting member of Figs. 4 and 5 alongthe line BA-BA;

.Fig. 7 is a cross-section of the head of Fig. 1A along the line l-1;

Fig. 8 illustrates a wiring diagram suitable for use with the invention;

Fig. 9 illustrates a guide member of a different form of the invention;

Fig. 10 is a cross-section of the guide member of Fig. 9 along the lineill-l0;

Fig. 11 is a top view similar to Fig. 1A of a modified form of theinvention;

Fig. 12 is a sectional side view of a magnetic recording reel mountingstructure of a further form of the invention;

Fig. 13 is a sectiona view similar to Figs. 12 and 10 of a still furtherform of the? invention;

Fig. 14 illustrates a wiring diagram suitable for use with the form ofthe invention illustrated in Fig. 13; and

Figs. 15 and 16 are diagrammatic representations of side and top viewsof another form of the transducing apparatus according to the invention.

In the wide use of home type magnetic recording and reproducingapparatus it is extensively possible for laymen to prepare very highquality magnetic recordings at home. Radio programs, for example, can beexcellently recorded on limp magnetic recording tapes having a stratumof bonding compound containing substantially uniformly dispersed thereinpermanently magnetizable powder particles, such as are described in thecopending applications of Otto Kornei, Serial Nos. 685,092 and 685,093filed July 20, 1946, which latter application has been abandoned. Forcertain purposes, as for example, when a desired .recording is notavailable in any other manner a reel of magnetic recording medium havingmagnetically recorded thereon such a recording may be purchased.Hitherto all magnetic recorders have been made with a single magnetictrack guide path for erasing, recording or reproducing. The ease ofmaking magnetic recordings or of erasing prior magnetic recordings mayoften be disastrous to a commercial recording which can easily be runthrough such prior recorders with the control switch inadvertently setto erase or record, and in a few minutes erase an expensive recording tonothing but a blank magnetic track which can be readily purchased atsmall cost, or superimpose another recording and thereby ruin theexpensive recording beyond recovery of anything but the blank recordtrack.

According to the invention this difiiculty is avoided by providingrecord track structures having an elongated record track channelsuitably held in compact form as for example, one record track reel orsheet and imparting to the record track structures of the commercialrecordings a characteristic to which the home type recording andreproducing apparatus is sensitive and whichdoes not permit thealteration of the recording. The features of the invention may beutilized with conventional reels of filamentary record track, withendless reels such asthose illustrated in the Miller application, SerialNo. 588,911 filed April 18, 1945, now Patent No. 2,426,- 838, grantedSeptember 2, 1947, or with a continuous record track forming spacedportions of a magnetizable sheet having an extended surface which moveswith respect to a transducing head, to magnetically link successiveportions of the surface, as described in the Williams application SerialNo. 651,637, filed March 2, 1946, which iSSIJlSgY-aS Patent Number2,426,838 on September 2,

In Fig. 1 is shown diagrammatically one embodiment of the inventionwherein a magnetic record track in the'form of a tape 3| is un- Woundfrom a supply reel 32 and wound onto a take-up reel 33. A magnetic headassembly structure 35 having a guide portion it is disposed so that therecord tape 35 is led over the guide portion (it and around a rotatingcapstan M. The capstan includes heavy portions and the tape contacts theroller portion of the capstan along a maximum amount of its periphery.The large moment of inertia of the capstan helps to impart constancy toits rotation, and the large area of contact with the tape provides gooddriving means for withdrawing the tape over the guide portion it of themagnetic head assembly structure 35, and for feeding the tape to thetake-up reel 33. A. limit switch assembly 36 is interposed in the recordtrack path to assist in controlling the record track reeling operations.The head assembly 35 contains three magnetic heads, an erasing head 43,a recording head 45, and a reproducing head 5.

The guide structure 68 provides an outer guide path 69 and an innerguide path Si, both guide paths coming together at their extremeportions. The reproducing head 55 is placed in contact with the combinedguide paths in that portion 62 of the head assembly 35 where the recordtrack 3! leaves the head assembly in its forward reeling path from thesupply reel 32 to the takeup reel 33, as indicated by the arrow.

The erasing head 43 and the reproducing head 54 are placed in contactwith the inner guide path 6! where it is separated from the outer guidepath t so that the tape iii in moving along the outer guide path 59, asindicated by the dashdot line 3l-l, does not contact the erasing orrecording heads 43, 64 and only contacts the reproducing head as. Inthis outer guide path 89 the record track is beyond the magneticinfiuence of the erasing and recording heads 13, 4, and erasing andrecording operations cannot be effected. Along the inner guide path, asindicated by the dash-double-dot line 3l-2, the record track contactsall three magnetic heads so that erasing, recording and reproducing, orany combination of these, may be efiected. The magnetic heads d3, 44, 35may be identical, each containing a magnetic core 48 surroundedtransducing windings 53, as is well known in the art. A sensing member52 mounted on a pivoted arm 55 is shown as interposed in the inner guidepath 5: for operation of a switch 55. The sensing member 52 may bepositioned to project through the fioor or a wall of the guide path, andbiased so as to be actuated by the presence of record track in the innerguide path, to a position which closes the switch 56.

Fig. 1 indicates a wiring diagram that may be used for controlling therecording and playback operations. One terminal of the windings of eachcore is grounded. The other terminal of the recording head 44 isconnected to the output of recording amplifier it, the other terminal ofthe playback head 35 being connected to the input of playback amplifier62, and the ungrounded terminal of the erasing head 43 to the output ofthe high frequency oscillator W.

A suitable signal source, such as the microphone 19, feeds the input ofrecording amplifier l8, and a signal reproducing device, such as theloud speaker 83, is fed by the output of reproducing amplifier 82, thecircuits being completed by the ground connections shown. A capacitor85] feeds some of the high frequency output of oscillator T5 to therecording head L d so as to provide the necessary A. C. bias forrecording.

Switch 3'? acts to selectively connect suitable power sources, indicatedby the circled 3+ signs, to the amplifier and via switch 56 to theamplifier i8 and high frequency oscillator Ti so that in the left-handrecord position, when rec- 0rd track is present in the inner guide path,the recording amplifier it provides a recording flux in the recordinghead 44, and the oscillator 11 simultaneously provides an erasing fluxin the erasing head :23 and an A. C. biasing flux in the recording head.The exclusion of record track from the inner guide path 6!, as byconstraining it to travel along the outer guide path 69, makes recordingand/or erasing impossible both 7 because the open switch 55 will preventoperation of the erasing and recording cores 3, 44 and because recordtrack in outer path 59 is not magnetically linked with these cores.

Either of these preventative features may be relied on without theother, if desired. The apparatus of Fig. 1 will, accordingly, besuitable without the auxiliary switch control responsive to the presenceof record track. The switch control may be employed by itself, in whichevent the magnetic cores may be placed along a common guide path such asposition 62 with only the sensing m mber 52 situated on one of twoselective guide channel portions such as iii and as. In the right-handplayback position the switch 3] disconnects the oscillator I? and theamplifier it from the power supply, and connects the playback amplifier82 with its power supply so that recordings may be reproduced in thereproducer 83. The switch 3'! in the intermediate position showndisconnects all power supplies so that the apparatus is inoperative.

The reels 32, 33, shown distorted as to size, are mounted on rotatableshafts 38, shown as having collars 38 upon which "the reels rest.Projecting from the upper surface or" collars 39 are pins 42 which areengaged by corresponding openings or the hubs of the reels and serve totransmit rotational forces upon the shafts of the reels. Suitable meansmay be provided for actuation of the shafts 38 and the capstan forefiecting the desired reeling operations as is well known in the art.

The selection of the guide path along which the record track moves isplaced beyond the control of the operator, as for example, by suitablyshaping the walls bounding the guide structure it so that record tracksof one shape will be moved along the inner guide path'fil, Whereasrecord tracks of other shapes will not be permitted to enter the lowerguide path SI and will be held away and move along the outer guide path69.

Fig. 1A is an enlarged View showing in greater detail the constructionof a head assembly 135 according to the invention. The head assembly I35may be molded or machined as an integral member having side walls 63 andthree laterally disposed openings 1W. Along the guide portion GB of thehead assembly I35 a deep channel I6! is provided, the door I59 of thischannel defining an inner record track guide path.

A portion of the walls 63 that define the sides of the guide channel l6!are hollowed, as indicated at in Fig. 2, to provide internal shouldersI66 extending over most of the length of the guide portions M3. Theshoulders H58 are situated externally of the 553 of the channel i3! anddefine the two marginal regions of another guide channel 59. The guidechannels i-fil, I69 are convexly shaped and the distance between therespective floors I59, I68 varies along the assembly structure I35 in amanner similar to that shown in Fig. 1, being at maximum in anintermediate zone and decreasing to zero at the ends of the channel.

Fig. 2 illustrates one form of sensing construcwall ill, as indicated inFigs. 1A and '1. Smaller passageways I12 extend through the wall I1Iaxially of and communicate with the openings I16.

Magnetic heads I86 are placed within the openings E15, as indicated inFig. 1A wherein only two of the heads, the erasing head 43 and theplayback head 45, are shown mounted in place. Each of the heads containsa magnetic core 38 which may be made up of two generally C-shaped thinpole pieces I43 mounted so as to form a substantially closed magneticpath inciuding two small non-magnetic gaps 53. Each of the pole piecesMS may be surrounded by a transducin winding 558-.

As Shown in greater detail in Figs. l, 5, 6 and 6A, the magnetic headI863 is formed by mounting the pole pieces I43 on a mounting member Ielso shaped as to receive the pole pieces I43 as well as the transducingwindings I50, the heads I88 being disposed so that one of the pole piecegaps 53 as well as the surrounding pole portions 54 are exposed alongthe general contour of the floor i59. The mounting member I8I is shownas a molded or machined unit having two generally flat sides lilil'eachwith a periphery which has convex regions I83 and flat regions I84 so asto provide, a contour which generally resembles that of openings Ilil.On each of the fiat sides are a pair of inwardly directed shoulders I81as wellas pole piece supporting structures I88. The pole piece supportsI83 integrally connect the opposing sides I9il of the mounting memberI85.

' tween the pole piece supports I88 and accommodates the windings I5ll.The pole pieces I43, intermediate regions of which carry the windingsI59, are mounted on the pole piece supporting structures I88 so that thewindings fit inside the groove wt and the pole portions 54 of the twopole pieces disposed near the fiat faces and are spaced by a suitablenon-magnetic gap. A small groove i953 may be provided in the pole piecesupporting structures its immediately below the non-magnetic gap regionso as to facilitate the adjustment of the gap. C-shaped leaf springs I95shown supported against pins fitting through openings I9? in the sidesI90 are shown as urging the pore pieces I63 against the pole piecesupports I88 so as to retain the pole pieces in place. Some of thelateral faces of the pole piece supports I88 may be cut away to providesmall wedge-shaped gaps I99 under the pole pieces I43. The urging byspring I95 causes thepole pieces to bend slightly into the gaps I99 andmakes for more secure assembly. I

The entire magnetic head construction is similar to that described inthe application of Otto Kornei, Serial No. 688,034, filed August 2,1946, which issued as Patent No. 2,523,576 on September 26, 1950, and ispositioned in opening I16 so that the shoulders Isl form a generalcontinuation of the surface of the floor I59 and the pole portions 54 ofthe pole pieces emerge above the fioor to a very small extent to providea slight amount of increased tension on the tape as it is impelled alonga guide channel. To help in such positioning of the magnetic heads, theopening I10 may be slightly larger than the mounting member NH and thepassageway I12 slightly larger than the boss I92 so that when afastening plate 280 containing corresponding apertures IE0 is mountedagainst the exposed side I and around the exposed bosses I92 the bosseswill project from both sides of the assembly structure 35 and can begrasped and moved to properly position the head before the plate 269 issecurely fixed in place.

As shown the reproducing head is mounted in the terminal portion of theassembly structure I 35 Where the channels are at the same level. Theerasing and recording heads are mounted in the floor 459 of narrowerchannel I6! in those regions where the ledges I68 are some distanceremoved from this floor I59, as shown. The magnetic heads may beidentical in which case they should be wide enough to accommodate thewider tape passing through channel Hi9 since the reproducing head mustoperate in conjunction with either tape. Such a construction isindicated in Fig. 7 wherein the extra head width does not interfere withits operation in the narrower channel I6I. It is obvious, however, thatthe reproducing head 45 may have a tape guiding width larger than thecorresponding width of magnetic heads 42 and 43.

With the arrangement illustrated commercial recordings on tape too wideto fit into narrow guide channel I6! may be obtained and run through theassembly structure I35 with no possibility of erasing or superimposedrecording taking place. On the other hand, there may also be obtainedreels of record tape narrow enough to fit into the guide channel IBI,and on such narrow tapes radio programs, telephone conversationsor othersound sequences may be recorded, erased and re-recorded at will. Anyinadvertent setting of the controls to record or erase will have noeffect on the wider tape.

In a practical construction, such as is shown in Figs. 1 through 7, theconvexity of the floor I59 of the narrower channel MI in the assemblystructure I35 is minimized so as to diminish the friotionalforcesagainst the tape as it slides along the assembly structure I35. With thesmall convexity of floor I59, not enough pressure is applied between thetape and the pole portions 54 of the magnetic heads, and pads I20 areprovided and mounted on pivoted arms l2I so disposed that by actuationof the arms lZI, into the operative position shown in dotted linesinFig. '7, the pads I251 will rest on the tape and press it against thepole portions 53 so as to maintain stable magnetic contact and linkagebetween the magnetic core and the successive elements of the magnetictape as they pass the gap 53. Enough freedom of rotation is provided forthe arms IZI so that in the non-operative position, shown by the solidlines of Fig. 7, the pads I20 are completely re.

moved from the guide channels to enable simple threading of the tapealong the channel. The pads may be made of felt or other soft resilientmaterial. The arms [2! may be ofiset, as shown in Fig. 3, so as not toobstruct the easy access to the adjacent projecting boss I92 and may bepivoted on a plate lZd attached to the lower side of assembly structure135. The assembly structure may be provided with fastening means, asshown, to securely hold it suitably positioned in the apparatus. Thedash-double-dot line 36 shown in Fig. 1A is the path along which thetape may be rapidly wound from one reel to an other without passing incontact with any of the magnetic heads. The path 36 may be used forrewinding or fast forward reeling. In the drawing the record tapethickness is greatly exaggerated in the interest of clarity.

The guiding of narrow tape through the narrow channel 165' willsatisfactorily center it on the reproducing head 43 which is onlyprovided with wider guides. If desired, however, additional narrow guidemeans may be provided on the capstan side of reproducing head 15, as forexample, by grooving the floor of the channel at this point to form anarrow tape guide channel 62 shown in Fig. 1A.

The windings of the magnetic cores may be connected, as indicated inFig. 8, wherein a pair of push buttons ll, 22 in the conventional twopush button assembly 15, control respectively the recording and theplayback operations. As is well known, the push button assembly is soarranged that either button may be pushed into its operative position,and that when one is pushed in the other is unlatched and pops out underthe action of a biasing spring. However, both buttons may be pushed inif simultaneously actuated.

On each core the windings are connected in series, one end of theerasing core windings being connected to an oscillator H and one end ofthe windings of the ecording core is is connected to the output ofrecording amplifier #8 in an arrangement similar to that shown inFig. 1. The playback core 25, playback amplifier 82, signal reproducingdevice 83, signal source I?! and variable coupling capacitor 88 are alsosimilarly connected. The B+ supply for operating the oscillator l? andthe amplifiers 78, 82 is indicated by the circled B+ in Fig. 8 and isled to these units through switches 86, 87 which are operated by theshaft of the push buttons H, 12 respectively, as shown. With the recordbutton pushed in and the playback button out the B+ is supplied to therecording amplifier l8 and the oscillator 7? so that a proper recordingof signals may be obtained. Pushing in the playback button 12 permitsthe recording button H to pop out and removes the 3-}- supply from therecording amplifier l8 and the oscillator ii, and establishes a B+supply to the playback amplifier 82, thus permitting the reproduction ofthe recording. By suitable manipulation both recording button 7! andplayback button i2 may be maintained in their operative inwardly pushedposition so that a recording may be made and. immediately played backfor monitoring or other purposes. In a practical embodiment of theapparatus the connections to the windings I59 may be made by means ofpins E95 mounted in one side I99 of the mounting member lat, the ends ofthe windings being led over notches 94 and fastened to pins I96.

Other operating means, suchas the second push button assembly 16, may beused to control the tape impelling means so as to operate the tape inthe regular forward direction for recording or reproducing, rapidly inforward direction for quickly locating a desired spot in a longrecording, or in rewind direction for rapidly rewinding. Driving means,such as motors, may be suitably mounted and connected with the supplyreel 32, take-up reel 33 and the capstan "ll, and may be suitablyconnected with switches operated by the push buttons of the assembly 16,Mechanical or electrical interlinkage may be provided for actuating thearms l2! when the forward push button is pushed so as to bring the pads:26 into contact with the tape to establish stable magnetic linkageswith the respective magnetic heads. A biasing spring i22 retracts thearms l2i into inoperative position when the forward push button is inits outer or inoperative position, as for example, when any of the otherbuttons of assembly '55 is pushed in. The assembly '16 may also containanother push button for stopping the impelling of the tape when desired.A lever as may be mounted adjacent the switch assembly it andmechanically linked with the arms 2| so that operation of the forwardpush button will rotate the lever 9i] and pull the pads I20 down intooperating position.

If desired, the recording and playback amplitier may be combined inwhich case the switch assembly '55 may be revised so as to suitablyconnect the altered amplifier input and output as required for recordingor playback position. With such construction a supplementary playbackamplifi r and a supplementary recording amplifier be used as taught inthe application by Otto Kornei, Serial No. 685,0? 2, filed July 20,1946, This application also shows the switching arrangement which may beemployed. at is, of course, understood that simultaneous recording andplayback cannot be eii cted with such a combined amplifier arrangement.

Figs. 9 and 10 indicate a guide structure or preventing inadvertenterasure of or superimposed recording on a commercial recording which itis desired maintain intact in accordance with the invention. A guidestructure 235' is shown as having two guide channels 26! and 2&9 in amanner analogous to the combined channel structure of Figs. 1 and 2.Shoulders 258 define the marginal regions in the floor of channel 289and in one of these shoulders is mounted a pressure sensitive follower27:3 which has a rounded upper surface and which is urged downwardly bythe marginal portions of tape wide enough to be held away from the lowerchannel 253 by the shoulders 2-68. This downward movement of thefollower 22% operates a switching arrangement 23 1 through lever arm273. The follower 2155 and the lever 2?:5 operate in passageways in theguide structure lever 2i3 being shown pivoted on a mounting plate 21 Eattached to guide structure.

In operation a tape is under tension, and in moving over the guidestructure 235 it depresses follower member 210, if of the necessarywidth, opening switch 234 so connected as to prevent the supply oferasing current to the erasing head as well as the supply of recordingcurrent to the recording head. Only two magnetic heads are required inthis construction, the recording head being used as a playback head byproviding suitable interchanging of leads by a switchingarrangementwhich may, for example, be similar to pole pieces of themagneticheads.

' that shown in the above mentioned Kornei'application. The curvedexposed portion of follower 2'10 may be a roller revolvably mountedaround a pivot fixed to the slidable lower portion. Two guide members235 may be employed with the combined erasin head and the transducerhead structure mounted between them, the guides then serving to properlycenter the tape over the The switch 234 may when actuated by thedownward urging of follower member Zlll merely open the 13+ supplycircuit to the oscillator and final recording amplifier.

The use of two guides of the type shown in Figs. 10 and 9 is necessarybecause in this construction the guide channels in the magnetic headsare too wide to properly center a narrow tape. The switch 234 may be ofthe micro type, requiring very little motion and force for actua' tion.

Fig. 11 shows a modified construction of the invention in which themagnetic heads 43, 54, 55 are. not mounted inside an integral head asisembly containing a record track guide, but are ing head' iii and therecording head it, as shown, and provide two record track channels 26!,269

in a manner analogous to that iown in Fig. 2. The second guide unit 2 39also provides two recrd track guide channels 262 and 2m in a similarmanner. The magnetic heads 43, M and 45 may be similar to those shown inFig. 1A, but may have their side walls extended upwardly to form recordtrack guiding members Pads I25 may be provided for better contactbetween the tape and the magnetic cores, as in Fig. 1A. The channels 269and 25! in guide unit 239 should be spaced far enough apart so that theoperation of the pads 129 does not interfere with the movement of therecord track in either the outer guide path 3l-3 or the inner guide path3ll.

The second guide unit 249 may have its guide channels 262 and are moreclosely spaced and even meeting in one portion, as shown, and may beplaced bet een the reproducing head 45 and the capstan roller 4|. I

So-called pe manent recordings may be made on tape too wide to movealong channels 125i and 252 so that it is directed into the outer guidepath 3l3 by the channels 269, 279 of the guide units 239, 240. Theguiding portions 2% of the magnetic heads G3, at may be wide enough toadmit only the narrow record tracks, and the corresponding guidingportions 2% of reproduc ing head 45 may be wide enough to receive thewide record tracks.

Threading of the tape for the operation of the apparatus may be efiectedby simply guiding the tape from the supply reel over the periphery ofthe two guide units 239, 249, then around the capstan roller ii, andfrom there onto the takeup reel in a manner similar to that shown in g.11. Beginning of the reeling operation will cause tensioning forces toappear in the portion of the f; record track between the supply reel andthe capstan roller 4!, and these tensloning, forces ping it at the outerguide path 3 1-3 if it is wider than thecritical width and permitting itto move W 10 to the record track path ill-4 if it is narrower than thecritical width. The guide unit 2% merely acts as an additional guidingmeans so as to properly center the narrow record tracks in their passageacross the reproducing head 45.

The apparatusof Fig. 11 operates in a manner similar to those shown inFigs. 1 and 1A, and may be used with the amplifiers shown in Fig. l orFig. 8.

The magnetic tapes of difiering widths may be supplied on reels orholders having difierent tape receiving dimensions but of the same,overall width. The narrow tape receiving spacing may be centrallydisposed with respect to the wide tape receiving spacing to insure theproper feeding of the narrow tape path along the transverse centralportion of the wide tape path. If desired, however, the tapes may besupplied on reels 0f-different overall widths, in which case two levelsof reel mounting may be provided on the reel mounting shafts 38.

According to another phase of the invention, inadvertent erasure orsuperimposed recording may be prevented by providing the supply reel 32with a specially shaped portion to which the transducing apparatus issensitive. With such construction. record tracks may be oi identicalphysical characteristics.

Fig. 12 shows one former such an apparatus. rotatable collar 39 andshaft 38 on which the reel 32 is mounted are driven by belt 9i!frictionally engaging pulley 9| affixed to shaft 38. The shaft 38 has acentral longitudinal aperture 92 extending through the entire shaft andreceiving rod 93. Slidablv mounted on a supporting member 94 under theshaft 38 is a follower 95 biased upwardly by a spring 95, as

lower as a switch 38 is mounted so that in the,

up position of rod 93 switch 98 is o ened, and when 93 is moveddownwardly "switch fit closed.

Reels 32 may be provided in two different shapes, one containing anaperture in the upper portion of the hub, as shown inFig. 12, and theother being imperforate in the corresponding location. Mounting of thereel having an aperture 99 will permit the rod 93 to proiect through theaperture 99 to its highest nosition, thereby leaving the switch 98 open.Mounting of a reel having no aperture corresnonding to the aperture 59wi l force the rod 93 downwardly to close the switch 98. The s itch 93may be connected with relay means lilfl to prevent the anplication oferasing or recording flux to the record track unreeling from the reel.

In the guide construction of Figs. 1A, 9 and 11 the outer guide-oathdefin ng shoulde s are, 266, or 269 act as sensing devices responsive tothe width of the tape for directing the wider tape along one path andpermitting the narrower tape to traverse another path.

Although Figs. 1 through 12 are shown as employed with record tracks inthe form of a tape, similar constructions may be used for wire typemagnetic record tracks in accordance with the invention. A wire guidepath ma be defined by a grooved guide structure in which the grooveadmits a narrow wire but does not permit the entry of a wider wire. Thepads l2! are unnecessarv fo use with wire type record tracks.

Fig. 13 illustrates another apparatus according structure 335 is formedb the upper cut-away region of the sid members 3%, M! which provide themarginal portion of a fioor generally continuous with the upper edge ofintermediate member 3 53. The magnetic record track used with theconstruction of Fig. 11 may be of the above mentioned type described inthe Kornei application, Serial No. 685,092, filed July 29, 1946, sincethe bonded magnetic powder layers of such a tape do not in general haveany appreciable electrical surface conductivity. Both commercial andhome recordings may then be made on tapes of the same width and ingeneral of the same physical characteristics with the exception that thetape used for home recording may have a thin superficial coating ofelectrically conductive material which contacts and electricallyconnects the side members S it and 3H to close a circuit which permitsthe application of erasing and recording current to the tape, Thecommercial recordings having no such electrically conductive coatingwill thereby be safeguarded against inadvertent damage.

The differentiating electricall conductive coating need only be appliedto a leader portion of the tape, such as the leader portion used forthreading, and the closing of the circuit between side members 34 3 3!may be interlinked with the recording controls in such manner that thesecontrols cannot be set to the record position without the action of arelay operated by the circuit through the side members. A self-lockingrelay placed in this circuit, in one instance, may be so connected as tohold the record switch in the record position from which it is otherwisebiased by a spring, and a reeling limit switch operated by the unrcelingof all the tape from a supply reel, for example, may unlock the relay.Alternatively, the electrically conductive coating may be applied overthe entire length of the tape in which case it is preferred to have theelectrically conductive coating on the surface of the tape which isopposite to the surface that contacts the magnetic heads. It is obvious,of course, that variou other types of electrically conducting guidemembers may be employed to make it unnecessary for the conductivecoating to extend the entire width of the tape.

Fig. 14 diagrammatically illustrates one form of a control apparatusaccordin to the invention. In this arrangement, the control may beexercised by a leader strip of tape attached to the reel of magneticrecording tape, which leader strip may or may not be provided with anelectrically conductive coating to determine whether Or not recordingshould take place. The guide unit 335 is similar to that shown in Figll, and the magnetic erasing head 2&3 and the magneticrecording-reproducing head 2% are positioned in the guide path definedby the guide assembly 335. A source of signals, such as the microphone2W, a sound reproducer, such as the loud speaker 283, amplifiers 2M, and262 as well as high frequency oscillato 2'3! are interconnected with therecording-reproducing head 244 through a multipole switch assembly 275which may be operated to a left-hand record position or a right-handplayback position and is biased toward the playback position by spring220. In the right-hand playback position, as shown in the figure, therecording-reproducin coil is connected to the input of main amplifier265], the output of main amplifier 260 is connected to the auxiliarycorrecting playback amplifier 262, the output of which in turn isconnected to the sound reproducer 283 by the various contacts of theswitch 215. In the left-hand record position the signal source 2'59 isconnected to the input of the main amplifier 259, the output of which isfed through the auxiliary correcting recording amplifier 26I to therecording-reproducing head 244 together with the output of a highfrequency oscillator 2Tb. The output of the high frequency oscillator27'! provides a high frequency A. C. bias for suitably recording theamplified signals originating in the signal source 219, as is well knownin the art. In the left-hand record position one of the switch bladesalso connects the erasing head 243 with a source of 60-cycle A. Ccurrent 22!, as shown. All the circuits are indicated as completed byground connections.

The erasin head 2 13 is so disposed as to provide in the path of themagnetic record track 3i a magnetic field which is relatively intenseand which has suitable decay characteristics so that each elementalportion of the record track 3i is subjected to a saturating magneticfield followed by at least about three cycles of decaying magnetic fieldand is effectively demagnetized for proper recording of the signal fluximpressed by the recording-reproducing head 244.

The multi-blade switch 215 is provided with an actuating member 225containing a cam-shaped projection 223 so positioned as to be engaged bya latch lever 228 when the latch lever is rotated around a pivot 229 tothe clockwise latching position shown by dotted lines in the figure. Thelatch lever 228 is biased to the counterclockwise position shown in fulllines, by the spring 25i,

and is rotated to the dotted clockwise position by the relay winding 252under the influence of the conventional electron tube relay circuitindicated. The relay circuit is so connected with the conductive sideplates 34D, 34! of the guide assembl 335 that when no electricallyconductive material joins the side plates 340, 34!, the relay windin 252is inactivated and the switch actuating member 225 cannot be retained inthe left-hand record position. On the other hand, when electricallyconductive material, such as a magnetic record track leader stripsurfaced with a conductive coating, contacts the conductive side platesare, 3M the relay winding 252 is activated, the latch lever 228 assumesits dotted line position, and the switch actuating member 225 may beretained in the record position.

The relay winding 252 is shown as provided with an additional switchblade armature 285 which together with its associated contact 28'! actsto shunt the relay circuit so as to lock the winding 252 in itsactivated, position even though the relay circuit through the guideplates 348, 3 is opened. A switch 288 is placed in this locking circuitand may be connected with a limit switch so as to open the lockingcircuit when the magnetic record track is moving in a reverse directionin its guide path, as for example, when is being rewound after a forwardreeling operation.

" place.

With the circuit of Fig. 14 a magnetic record track provided with anelectrically conductive leader strip may be threaded al ng a guide pathso that the leader strip contacts the side plates 34B, 3 1! of the guideassembly 345, and the switch 275 may then be placed and maintained inits record position so as to enable erasing and/or recording on therecord track. The circuit will maintain the switch 2'55 in the recordposition until such time as the record track movement is reversed toopen the switch 288'. A record track provided with a leader strip thatis not electrically conductive will not permit the maintenance of theswitch 275 in the record position so that the record track willnot beinadvertently erased or have another signal superimposed.

Any other physical property may be used for controlling the erasingand/or recording on a record track. Light reflecting properties may bealtered by suitable coatings and may be used in conjunction withphotoelectric cells as a sensing device. Furthermore, the recording me-,dium may be provided along one edge with a series of perforations and asource of light so placedthat an interrupted beam through theseperforations will impinge on a photocell and sup ply current to actuatea relay which requires actuation for rendering the apparatus capable oferasing or making new recordings.

The specific inductive capacit of the tape may tapes or tapes having anunsuitable dielectric constant.

A further modification according to the invention is one in which asignal may be superimposed on the signals to be recorded and may be usedto operate a sensing device responsive to this signal in the playbackoutput for controlling erasing and/or recording operations. This controlsignal should be of a frequency outside the desired frequency playbackresponse limits but within the pick-up limits of a magnetic pick-uphead. The frequency of the control signal should not be high enough tobe of erasing or biasing frequency, nor low enough to be undetectable.

filtering stage may be interposed in the playback circuit to segregatethe control signal so that it does not appear in the final output and tofeed the control signal, amplified if necessary, to relay meanscontrolling erasing and/or recording circuits. A special reproducinghead may be provided so that the recording medium has to pass this headbefore it reaches the erasing and recording heads. This special head maybe designed for maximum response to the control signal frequency. If thecontrol signal appears on the tape erasing and recording may take Therecording apparatus of home recorders may be equipped to superimpose thecontrol signal during a recording process. If desired, the controlsignal may be manually controllable so that it may be omitted when thehome recorder is to make a permanent recording.

The pole face width of the erasing core may 14 be wider than thecorresponding widths of the recording core and playback core to insurethat all recording and playback be effected on record track that hasbeen properly erased. Furthermore, when different recording and playbackcores are used, as shown for example in Figs. 1 through 8, it is highlyadvantageous to make the pole face width of the recording core differentfrom the corresponding width of the playback core. Making these cores ofthe same width permits slight variation in alignment of one core withrespect to the other to greatly effect the playback level since part ofthe recorded signals will be out of range of the playback core. However,a difference in width enables the maintenance of constant playback levelin spite of appreciable misalignment. 1f the pole faces of the recordingcore are the wider ones, the playback pole faces will respond to aconstant width of recorded signals so long as the misalignment tillmaintains the playback pole faces within the limits of the width of therecording pole faces. if the playback pole faces are the wider ones,entire recorded signal width will be played back so long as misalignmentstill maintains the playback pole faces spanning the entire width of therecording pole faces. Fig. 15 shows one suitable arrangement oftransducing cores in which the record track 3! moves in the directionindiby the arrow across the erasing core 43, the recording core 44 andthe playback core 45.

in place of the magnetic cores shown in Figs. 1A and 4 through 6A, othercores such as those shown in the Begun application Serial No. 688,738filed August 5, 1945, which issued as Patent Number 2,513,617 on July1950, may be used. The ring shaped cores formed of only a singlelamination of sheet metal of a thickness of the order of four tofourteen mils, having only a small non-magnetic gap, and extendingsubstantially entirely on one side of the record track guide path areespecially useful in that they are extremely sensitive and eflicient.

According to another form of the invention, the transducing head may bearranged for operation with record tracks of two different widths byproviding guide surfaces disposed so as to have the narrower width alonga marginal portion of the wider width. This is especially useful wherethe wider record track 13 about twice as wide as narrower and can supplytwo recording channels, one in each of its marginal regions.

15 diagrammatically indicates such construction in which the transducinghead 333 has the erasing, recording and reproducing cores 23, 41 i and45 respectively mounted along a lateral half of the record track guidepath Separate guides 5235 may be mounted on both sides of thetransducing head 333 to provide a wider and the narrower channel em asshown. In narrower channel 3%! a sensing member Zll) be located as shownin Figs. 9 and 10 for example.

sensing member 2% may be connected so that when engaged by a narrowrecord track it causes actuation of the erasing core #23 as well asording core the narrow record track being i taneously lead into magneticlinkage with the cores. The wider record track 3 i, as illustrated, islead through the wider guide paths 359 and and out of contact with thesensing member fill. According to this form of the invention, the widerrecord tracks may be provided with two non-erasable recordings, one ineach lateral half, so that after it is completely reeled through .a

transducing operation, the reeled-up record track may be lply turnedaround and re-reeled from th supply reel mounting to transduce arecording on the second channel.

This procedure is similar to that used in ing eight millimeterphotographic on a film track sixteen millimeter wide. An importantadvantage in this form of the invention is that a time-consumi ewindingoperation may be disany instances.

IL desired, tne commercial non-erasable cordings may be prepared on thenarrower tape with corresponding modification of the connections to thesensing member 2'15. As illustrate the erasing core 43 has a pole facewidth larger than that of the play-back core d5, which in turn is larthan that of the recording core l i, as indicated above.

With this operation, the record track reeling should be so arranged thatthe unwinding from the supply reel be in the same direction as thewinding on the take-up reel, as shown in Fig. 1A for When on iloying arecord track in the form of a non rna netic carrier having a bondedcoating of agnetizable particles, the sender): coating should be on thecore side of the carrier transducing from either channel and a reelingsuch as is shown in Fig. 1 wi l effect r ve 'sal of the coatingposition.

The guides may be incorporated as part of a unitary assembly structureincluding he transducing head, shown in Fig. 16 where the ends of theguide path of the assembly provide the two-l vel guide regions 335. Witheither construction both the wider and narrower record tracks aremaintained in contact with all the magnetic cores during any reelingalong the guide path or 338, inadverent damage being cad-r5 prevented bythe action of the sensing member erstood that the desired distinguishlcharacteristic to which the sensing de ice is responsive for controllingthe recordand/or circuits may be imparted to either the commercialnon-erasable recording or to tr e home type erasable recording, thecontrolling circuits being suitably adjusted. When the presence of thedistinguishing physical characteristic may be accidentally simulated itmay be prefe ed to use this physical characteristic snt to preventrecording.

be apparent to those skilled in the art that the novel principles of theinvention dis ed herein in connection with specific exemplithereof willsuggest various other modis and applications of the same. It is accord'ly desired that in construing the breadth nded cla p cific exempiiications of the invention bed above.

way for transducing magnetic record signals by magnetic inter inkagebetween said windings and successive portions of said record member;said record transducing means including control means settable in arecording condition for causing said head means to impress through saidcore elements a magnetizing flux and record magnetic signals onsuccessive portions of 2. record member impelled along said guideway;said control means being also settable in a reproducing condition forcausing said record transducing means to reproduce magnetic signalscorresponding to magnetic flux signals impressed by successive portionsof a record member moving along said guide way; said guide structurebeing arranged for interchangeable cooperation with a first recordstructure and also with a second record structure, each of said tworecord structures comprising a permanently magnetizable record memberwhich is impelled in an operative record transducing condition al ngsaid guide way for reproducing magnetic signals from a record member ofeither of said record structures when said control means is set in areproducing condition, and one of said. two record members having atleast one physical distinguishing element Zifferentiating said onerecord member from the other record member; said guide structureincluding preventive means having at least one sensing element m ansconnected to said preventive means and responsive to differentiatingaction of distinguishing element for actuating said preventive means toprevent the record member of one of said two record structures frombeing exposed to a magnetizing flux of said core elements and preventmagnelization of the record member thereof while impelled along saidguide way during a record transducing operation irrespective of thesetting of said control m ans.

2. In a magnetic record transducing apparatus for recording orreproducing signals on moving permanently magnetisable elements of amagnetic recording medium: a guide structure including guide elementsand impelling means for impelling a record member along a predeterminedguideway during a record transducing operation; record transducing meansincluding head elements having transducing windings and magnetic coreelements interlinked with said windings and having exposed magneticcoupling surface elements through which said windings are interlinkedwith successive surface portions of a record member impelled along saidguideway for transducing magnetic record signals by magneticinterlinkage between said windings and successive portions of saidrecord member; said record transducing means includin control meanssettable in a recording condition for causing said record transducingmeans to impress through said core elements a magnetizing flux andrecord magnetic signals on successive portions of a record memberimpelled along said guideway; said control means being also settable ina reproducing condition for causing said record transducing means toreproduce magnetic signals corresponding to magnetic flux signalsimpressed by successive portions oi record member moving along saidguide way; a first permanently magnetizable record member and a secondpermanently magnetizable record member for interchan eable engagementwith said guide structure to be impelled in an operative recordtransducing condition along said guide way for reproducing magneticsignals from 17 either of said two record members when said controlmeans is set in a reproducing condition; one of said two record membershaving at least one physical distinguishing element which is absent fromthe other record member and which differentiates said one record memberfrom the other reco member; said guide structure including -preventivemeans having at least one sensing-element means connected to saidpreventive means and responsive to differentiating action of saiddistinguishing element for actuating said preventive means to preventone of said two record members from being exposed to a magnetizing fluxof said core elements and prevent magnetization of the record memberthereof whi le impelled along said guide way during a record transducingoperation irrespective of the setting of said control means.

3. In a magnetic record transducing apparatus as claimed in claim 1 anelement of one of said two record members having an electric conductivity difierentiating said one record member from the other recordmember and said sensing element bein responsive to the differentiatingaction of said electrical conductivity of said distinguishing element ofsaid two record members.

4. In a magnetic record transducin apparatus as claimed in claim 3,substantially the entire magnetic core structure of said core elementsbeing' held along one side of the record member impelled-along saidguide way, so that each of I said record members may be freely removedfrom 18 impelled along said guide way, so that each of said recordmembers may be freely removed from its operative position along saidcore members. 7. In a magnetic record transducing apparatus as claimedin claim 2, an element of one of said two record members having anelectric conductivity difierentiating said one record member from theother record member and said sensing element being responsive to thediiferentiating (action of said electrical conductivity of said dis-'tinguishing element of said two record members.

8. In a magnetic record transducing apparatus as claimed in claim '7,substantially the entire magnetic core structure of said core elementsbeing held along one side of the record member impelled along said guideway, so that each of said record members may be freely removed from itsoperative position along said core members.

9; In a magnetic record transducing apparatus as claimed in claim 2, anelement of one of said two record members having a magneticcharacteristic difierentiating said one record member from the otherrecord member and said sensing element being responsive to thedifierentiating action of said magnetic characteristic of saiddistinguishing element of said two record members.--

10." In a magnetic record transducing apparatus. as claimed in claim 9,substantially the entire magnetic core structure of said core elementsbeing held along one side of the record member impelled along said guideway, so that each of said record members may be freely removed fromits'operative position along said core members.

S. J. BEGUN.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number

